No. I.] THE VERTEBRATE EAR. 287 



air and not from the vibrations of the sohd body of the micro- 

 scope transferred from the piano through the floor. 



It was found that vibrations of the intensity of loud notes on 

 the piano were only with difficulty transferred to the liquid 

 medium on the slide and to the hairs of the cochlea. They 

 were, however, transferred in sufficient degree to set in motion 

 the hairs while not affecting the basilar membrane fibres. Reiss- 

 ner's membrane also accompanied the hair band in vibration, as 

 might have been expected, but in these experiments was present 

 only as loose filaments floating on the liquid. 



The vibrations were immensely increased by placing the 

 stand of the microscope on the framework of the piano ; in fact, 

 so great was the degree of motion that the hair band disap- 

 peared from focus as a body, leaving a faint haze to indicate 

 its presence. Just as the vibrations of a steel rod fixed at one 

 end, when set in rapid motion, are not individually distinguish- 

 able, and the rod itself not visible, but appear blended into a hazy 

 band or fan-shaped body, so when the hairs vibrate to a tone, 

 as O, the agitation is so powerful and the oscillation so rapid 

 that the hairs are not visible and the individual excursions not 

 distinguishable. As the tone is allowed to die out, the haze 

 disappears more and more, and finally the hairs return to rest 

 and focus. 



That the hairs of the band vibrate individually we are assured 

 by repeated experiment, but that they are differential in their 

 responsive action to various wave lengths or periods we have 

 not been able to satisfy ourselves by direct observation ; but 

 we doubt that such is the case, for reasons to be presented later. 

 This much may be said, however : the hairs of the middle and 

 outer end of the hair band are longer than those of the lower end, 

 and the shortest hairs are in the end sections, so that theoreti- 

 cally we would expect the end sections, both proximal and distal, 

 to respond to the higher notes, on the assumption that there is a 

 differential action in the cochlear hair band regarded as a purely 

 physical body, while the centre of the mid-region would be 

 responsive to the lowest notes, grading off towards the higher 

 in both directions. When we remember that high notes are 

 much more valuable to the animal economy than the low ones, 

 and that the tones of the middle group of the commonly used 

 musical sounds are the most powerful in their effect (not the 



